1. Field of the Invention
The present invention generally relates to conducting and dissipating heat from a light source, more particularly to effectively dissipating heat from a light source via a heat conducting element and an independent heat dissipating element further allowing for economical replacement of an optics module at the end of the lifespan of the light source disposed within the optics module.
2. Background Art
Over the past century, a variety of different types of light bulbs and other light sources have been developed. The most common type of light source is the incandescent light bulb, in which electric current is passed through a metal filament disposed in a vacuum, causing the filament to glow and emit light. Another common type of light bulb is the fluorescent light.
The main problem with the standard light bulbs having resistive heating elements (e.g. tungsten) is that such a light source expends more energy as heat than as light. Fluorescent lamps run substantially cooler, but have a substantial lag time between when they are initially turned on and when they actually start emitting light, and are often fairly bulky. Halogen lamps are highly efficient, but need to be handled very carefully and generate a considerable amount of heat when manufactured large enough to provide a usable amount of light, even when powered with low voltage (e.g. 12V).
The most recent developments in lighting technology involve the expanded use of light emitting diodes (LEDs) that are quite efficient in that they are able to convert virtually all of their supply voltage into light, thereby producing less heat and requiring less overall power consumption. In addition, LEDs may be very small and have an extremely long service life, mainly due to the fact that they operate at cooler temperatures. Compared with a traditional light bulb, an LED lamp may have a lifespan of about 50 to about 100 times that of the traditional light bulb, and the power consumption of such an LED lamp may be about one third to about one fifth that of the traditional light bulb.
General LED light sources are well known in the art. LEDs are light sources based upon a semiconductor structure, specifically a diode structure, which emit incoherent light (which may be in the ultraviolet, visible, or infrared spectrum) when electrical current is passed through the semiconductor junction. One example of such a light source may include phosphors emitting white light. The original uses of LED light sources were in low-power applications such as indicator lights on instrumentation panels and the like. However, recent developments in LED technology have increased the output power and efficiency of LED sources so that it is now feasible for them to be utilized in traditional lighting applications previously reserved for incandescent, fluorescent, sodium, and known lighting technologies. Commercially available LED light sources surpassed incandescent light sources in terms of efficiency in or around 2002. More recently, commercially available LED light sources have exceeded fluorescent light sources in efficiency. Fluorescent light sources typically exhibit around 100 lumens per Watt (lm/W) efficiency; however LED light sources recently introduced into the market exhibit 130 lm/W efficiency, and there are other LED light sources available and currently under development which exhibit even greater efficiency. Since LEDs have the foregoing advantages, the LED lamp is expected to replace current conventional light bulb technology in the 21st century and become a new light source for illumination while concurrently providing other power-saving and environmentally friendly advantages.
One current drawback with such LED lamps is that when used to replace a conventional incandescent bulb they must have special driving circuits that convert the incoming alternating-current line voltage to the direct-current low voltage needed by the lamp. Such a circuit is normally a small printed-circuit board that is permanently mounted right in the lamp and to which the LED is normally directly soldered. These circuits typically incorporate a transformer to step down the incoming voltage and a rectifier and similar power-supply elements that produce the necessary steady low voltage.
The problem with such a construction is that the driving circuit itself generates heat, particularly when the LED requires some meaningful amperage, albeit at low voltage. Above a temperature of about 25 degrees Celsius, an LED operates less efficiently and produces less light than at lower temperatures. In particular, as the operating temperature progressively increases above 25 degrees Celsius, the light output of the LED progressively decreases. Since the LED itself is typically carried right on the circuit board, when the circuit elements heat up, the LED is heated. Unfortunately the efficiency of an LED falls off rapidly as it gets hot, and thus known LED lamps tend to dim somewhat after they have been in use for a while and their driving circuits have gotten warm. Such a limited conventional design is depicted in FIG. 1, wherein a general light emitting diode 10 integrates several light emitting diodes 20 sealed by a glass cover body 30, which has difficulty in dispersing the heat generated by the light emitting diode 20 during light emission. Such light emitting LED lamps cannot typically operate under normal conditions and tend to have high failure rates.
As the output power of the commercially available LED light sources continues to improve, it has become necessary to develop methodologies and structures for removing the heat generated by the LED from the LED semiconductor junction. Typical problems caused by heating of the semiconductor junction and surrounding structure are: 1) failures brought on by such occurrences as non-homogenous distribution of the current density over the junction (“current crowding”), which causes a local hot spot in the diode junction leading to early failure due to thermal runaway; 2) nucleation and growth of dislocations in the active region of the diode in which the radiative recombination occurs due to the existence of an existing defect in the semiconductor crystalline structure and which is accelerated by heat; 3) degradation of materials utilized in the LED, such as phosphor, causing loss of efficiency and changes in output color; and 4) electromigration of metal atoms at the metallization layers of the diode causing growth of conductive “whiskers” and early failure. This is not a complete list of the undesired effects brought on by elevated temperatures; it is provided herein simply as a list of exemplary effects.
In order to manage heat, the prior art has attempted to utilize a variety of heat dissipation techniques, such as the incorporation of heat sinks, heat pipes, fans, water flow, and the like. An LED may be attached to a heat sink via heat conductive adhesive, but if the LED stops working, then the entire component must be discarded, making parts replacement costly. Such LEDs are not exchangeable or serviceable and are therefore rendered disposable and very inefficient.
Attempts have been made to provide structures for removing heat from the semiconductor junction of LED lamps. See, for example, U.S. Pat. No. 7,226,189 (wherein heat produced is conducted to a heat dissipating device through a metal substrate and then conducted from the heat dissipating device to the light bulb base in an attempt to effectively disperse the heat via structures within the light bulb); U.S. Pat. Appl. No. 2006/0050514 (wherein the base of a bulb is a passive heat sink fittable into a socket); and U.S. Pat. Appl. No. 2006/0061997 (wherein an LED is clamped to a heat sink to permit the LED to be removable and replaceable, thereby making a serviceable LED assembly with an exchangeable LED). The inventions of U.S. Pat. No. 7,226,189 and U.S. Pat. Appl. No. 2006/0050514 are directed at attempts to better conduct heat away from an LED semiconductor junction within an LED lamp via incorporation of heat conductive material within the LED lamp, however, neither reference discloses a means or additional structure to dissipate heat from the socket of the disclosed LED lamps. U.S. Pat. Appl. No. 2006/0050514 discloses a means of clamping an LED circuit board to a heat sink but fails to disclose a heat sink independent from an optics module, wherein the optics module contains the driving circuit and a plurality of LEDs therein.
Further consideration must be made in that it is typically necessary for an LED light source to contain some circuitry that will take standard household electrical power and convert it to a voltage and/or waveform that is suitable to drive one or more LEDs. Consequently, a relevant design consideration may be beneficially included to allow for packaging of such circuitry within the LED light source or removable optics module.
It may be advantageous if the LED lamp has the size and shape of a standard light bulb, including a standard base such as the type of base commonly known as a medium Edison base. However, due to spatial and thermal considerations, many manufacturers have placed the circuitry at a variety of different location, where such designs may alter the size and/or shape of the lamp so that the size and/or shape differ from that of a standard light bulb. For example, the bulb may have a special cylindrical section that is offset from the base and therein contain the circuitry.
It is also a further desirable consideration to operate the present inventive illumination apparatus and other similar devices at as close to room temperature as possible. A heat conducting element and/or a heat dissipating element may therefore preferably be deployed in such an apparatus in order to remove heat from the LED in an effort to operate the LED as close to room temperature as practicable.
It is therefore desirable that modern light sources should make use of the currently available LED technology due to the significant benefits that such light sources provide including extremely long life, the ability to control output power and spectrum, and a significant reduction in the amount of electrical energy consumed for equivalent light output power. It is also desirable that such light sources be fabricated from materials that are inexpensive and preferably comprise re-usable, recyclable, or replaceable components so as to require a minimum of new raw material and thus preserve limited natural resources. However, utilizing LED light sources in modern light sources gives rise to the significant challenge of removing the heat from the LED semiconductor junction and surrounding structures. It is therefore desirable, and not currently known in the art, for an illumination apparatus to comprise an optics module containing a integral heat conducting element and an independent heat dissipating element, preferably wherein the integral heat conducting element is a component of an optics module that may be serviced and/or replaced separate and independent from the heat dissipating element so as to be environmentally friendly and lower overall maintenance and/or replacement costs for such present inventive illumination apparatus.